I've done some research and I came across a few threads here, but I have a somewhat unique situation.

What I have is a duty-cycle controlled DRL system in a car, (I unfortunately do not know the frequency of this signal yet). So what happens is the high-beam bulb (12V 65W), is in one of 3 states: off (0V), on (12V), or DRL (12V pulsed to give approximately 50% light output).

What I need, however, is to turn on a control solenoid when the high beams are on (constant 12V), but I do not want it to see any voltage in the other 2 states (off or DRL). Obviously off is easy enough, but the solenoid would be damaged by the duty-cycle control, so I need it to not be getting any power when the high-beam bulb is in DRL mode.